Sleep is a complex process that takes place in many stages. There are two basic phases of sleep, REM and NREM, in turn, each of which is divided into several sequences. Sleep cycles repeat a couple of times a night, with their number and length depending on a couple of factors, such as age and total sleep length. During the different phases of sleep, our brain works with varied activity. What characterizes the different phases of sleep? How long should deep sleep last in order to get proper sleep and good recovery?
Healthy sleep an important part of a healthy lifestyle
Sleep takes up almost a third of our entire life. The optimal amount of sleep for an adult is 6 to 8 hours, depending on the body’s individual predisposition and needs. Unfortunately, in today’s world, where a fast-paced lifestyle is the standard, very many people experience frequent (or constant) sleep deficiencies. This translates into frequent daytime malaise, deterioration of mental performance and physical well-being, and increasing health problems. This is the result of disruptions in the body’s recovery process.
What are the symptoms of sleep deficiency?
- Constant fatigue, lack of energy and desire to act,
- sleepiness during the day,
- irritability,
- mood swings,
- slower thought processes, lower mental productivity,
- impaired concentration and memory,
- distraction,
- absentmindedness,
- slower performance of daily tasks,
- trouble with decision-making,
- headaches,
- weakness,
- vision problems,
- congestion of the eyes,
- bruises under the eyes,
- gray, sallow complexion,
- easier and faster formation of wrinkles,
- decrease in immunity,
- hormonal disorders,
- excessive appetite,
- trouble maintaining a normal body weight, easier weight gain.
Sleep deficits occur most often in people who live fast-paced, busy lives, as well as those who lead irregular lifestyles and go to bed very late at night, such as. after sitting at a computer or in front of a TV or smartphone screen for long periods of time. Sleep deficiencies also occur in people who struggle with sleep problems, shallow sleep and frequent awakenings.
There is no doubt that reducing sleep deficiencies and regulating the diurnal rhythm is a recipe for improving psychophysical condition and ensuring a high level of vitality and energy on a daily basis. What exactly, from the point of view of physiology, is sleep?
What is sleep?
Sleep is a state of the body in which we experience a periodic loss of consciousness, a decrease in the activity of the nervous system, a decrease in motor activity, partial inertia and a decrease in sensitivity to external stimuli.
When we fall into sleep, the entire body rests and renews itself. Micro-damage in the brain caused during the day is repaired and all information is organized. The formation of new connections in the central nervous system also occurs. Cells throughout the body undergo regeneration. The state of sleep is accompanied by a slowdown of physiological functions.
Our biological clock functions in such a way that we fall asleep during the night hours, when sunlight does not reach our visual apparatus, and wake up to activity in the morning. If the diurnal rhythm is disrupted in any way and we don’t provide the body with the right amount of sleep at the right times, this results in inadequate recovery of the body and worse mood.
Even one-time sleep deprivation is associated with weakening of the body, exhaustion and deterioration of brain function, let alone talk about chronic sleep deficits. How does the sleep cycle work? How to sleep healthier and more efficiently?
Phases of sleep
What phases of sleep do we distinguish?
Sleep consists of two main phases – the REN phase and the NREN phase. The NREN phase occurs immediately after falling asleep. It is divided into 4 stages, after which the sleeper enters the REN phase. After the REN phase is over, NREN occurs again.
During the NREN phase, the sleeper enters a restorative deep sleep, while the REN phase is a shallow sleep phase (during which brain activity increases), which means that it is much easier to wake up from it.
Sleep phases vs. sleep cycles
The REN and NREN phases together form a single sleep cycle. Such cycles repeat several times throughout the night. Most often, we go through several sleep cycles each. Each complete sleep cycle is followed by a momentary unconscious awakening, after which we move on to the next cycle. The number and length of awakenings is largely influenced by the age of the sleeper. In elderly people, awakenings between sleep cycles are more frequent and longer, and the deep sleep phase is shorter. What can be noticed, in seniors the need for sleep also decreases and the tendency to get up very early increases.
How much sleep to get?
An adult needs about 6-8 hours of sleep. How does this translate into sleep phases and cycles? It is considered that to get a good night’s sleep, one should go through each sleep phase at least 2 times, i.e. 2 full cycles. However, the optimal amount is 4-6 cycles. The shorter the duration of sleep and the greater the disruption of the sleep phases, the lower the body’s ability to fully recover.
How long do the different sleep phases last?
The length of the different phases varies depending on how long it has been since we went to bed. The longer we sleep, the shorter the deep sleep. In the first half of the night (in the first, second and third sleep cycles), the phases of deep sleep are prolonged. In contrast, in the second half of the night, after going through three cycles, deep sleep is shortened or even absent altogether, while the REN phase and the middle stage of the NREN phase – N2 – are prolonged.
The NREN phase is much longer than the REN phase. It lasts approximately 80-100 minutes. In contrast, the REN phase lasts only up to 15 minutes in the first cycle and up to about 30 minutes in subsequent cycles.
The initial stage of the NREN phase, which is also a transitional state between waking and sleeping, or falling asleep, usually lasts a few minutes. Then we enter a 20-minute stage that prepares us for deep sleep, and finally fall into a healing, mind- and body-renewing deep sleep.
How long should deep sleep last?
As we sleep, deep sleep becomes shorter and shorter in successive cycles. In the first cycle, it may last as long as several tens of minutes, and in the last cycle it may take only a few minutes or even disappear altogether.
Exactly how long should deep sleep last? There is no single answer here, as every body is different and needs a different amount of sleep. Much depends on individual conditions of the body, lifestyle, age. There is also a relationship between the length of deep sleep and the overall quality of sleep. If we sleep without problems and sleep the right amount of time (about 7-8 hours), deep sleep usually lasts long enough. In contrast, if we struggle with insomnia or other sleep disorders, our sleep is shallow, intermittent, the length of deep sleep is usually insufficient.
In general, deep sleep should last long enough for the body to rest well and be fully regenerated. If we get up sleep-deprived and deprived of vitality, perhaps the sleep phases are disturbed in us and deep sleep lasts too short. Fortunately, there are simple methods to increase the efficiency of night rest and prolong deep sleep.
How to prolong deep sleep?
Physical activity is one of the more effective natural remedies for sleep problems. After taking a dose of exercise, we feel relaxed, de-stressed and pleasantly tired. The whole body relaxes, circulation improves, breathing evens out, and the mind frees itself from negative emotions. All this makes it easier and faster to fall asleep and enter a healing, deep sleep for a longer period of time.
A regular lifestyle
A disrupted sleep schedule has a negative impact on the quality of our rest. If we want to prolong deep sleep and thus improve recovery, wake up with lots of energy and with a good feeling, let’s try to regulate our diurnal rhythm as much as possible. To this end, it is worth trying to always go to bed at a similar time and get up at a similar time. On the other hand, you should avoid sitting up late at night, getting up around noon, lying in bed for long periods of time after being awake.lying in bed after waking up, and taking naps during the day, especially prolonged ones.
Good mattress, good pillow
Prolonged deep sleep is also fostered by taking care of technical issues related to sleep, that is, what we sleep on and the conditions in our bedroom. Let’s take care of good darkness in the room and absence of noise, so that no external stimuli disturb the continuity of our sleep. Let’s get a comfortable, good mattress and a comfortable, ergonomic pillow, giving good support to the head and cervical spine and providing relaxation to the body. Pillows with natural filling, for example, including a pillow with buckwheat husk, work great here.
A portion of relaxation before bedtime
To increase the comfort of sleep and improve the efficiency of deep sleep, it is also worth taking care of the evening de-stressing, calming down, relieving tensions and strong emotions and entering a state of inner harmony. Relaxation music, meditation, small stretching exercises, visualizations, breathing exercises, reading light, cheerful literature can be very helpful in this regard.
What are the different phases of sleep?
NREN phase
The NREN phase is a stage of sleep during which physiological functions slow down and the whole body undergoes intensive recovery processes. The NREN sleep phase is divided into 4 stages such as:
- Stage N1 – the moment of falling asleep, that is, the transition from java to sleep. Slow eye movements appear. Alpha brain waves die out, while theta waves appear. Less and less external stimuli reach us, the body relaxes, thoughts become disjointed and chaotic, consciousness slowly leaves us.
- Stage N2 – we are already in a dream state and have no consciousness, our body is preparing to enter deep sleep. The body temperature slightly decreases, the heart begins to beat more slowly, the heart rate becomes more steady. However, sleep is still shallow and it is quite easy to wake up.
- Stage N3 – the deepest sequence of sleep, from which it is very difficult to wake us up. The respiratory rate decreases, there is full relaxation of the muscles, blood pressure drops. In the recording of bioelectrical activity of the brain, high-voltage delta waves of electrical activity of the brain can be noted.
- Stage N4 – the so-called slow-wave sleep which is the deepest stage of sleep. The eyeballs do not move. On the EEG can be noted the dominance of delta brain waves. In the N4 stage, daydreams may occur, but they are less vivid and less frequent than in the REM stage.
REN phase
The REN phase is also known as paradoxical sleep or rapid eye movement phase. It is an active sleep during which dreams occur. At this stage, sleep is shallow and the sleeper is prone to awakening. While the NREN phase is for deep recovery, the role of the REN phase is mainly to consolidate memory traces, stabilize emotions and regulate neurotransmitter levels.
